SignUpGenius
Free version includes:
- multiple spots in one time slot
- email (ics) confirmation to invitee
- export as table
- cancellation email triggered by organizer
- modify bookings by unique link (in the email).
UX feels like oldest.
Doodle
Free version includes:
- multiple spots in one time slot
- export as table (maybe?)
No invitee email is available in free version. Booking modification can only be protected if invitees log in with a Doodle account. UX is a lot better.
Calendly
Free version includes:
- email (ics) confirmation to invitee
- export as table
- cancellation email triggered by organizer
- modify bookings by unique ID (in the email)
Paid version (10 days trial) includes:
- multiple spots in one time slot
- webhook (API)
UX is the best.